Many water sources that are used by consumers for personal care contain elevated levels of calcium and magnesium salts, as well as undesirable levels of redox metals (e.g., copper and/or iron) salts. As such, using chelants to sequester trace redox metals often proves to be ineffective because most chelants also competitively bind calcium and/or magnesium.
It has been found that even trace quantities of these copper can deposit on the hair surface and in between the cuticle layers of hair. This deposition of copper on hair is especially problematic because transition metal ions, such as copper and iron, can facilitate reduction-oxidation (redox) reactions during hair coloring treatments and during UV exposure. These reactions generate reactive oxygen species (ROS), which in turn can cause damage to the hair. In addition, they can interfere with the oxidative color formation chemistry and lead to reduced color uptake for hair colorant users.
Accordingly, there is a need for improved shampoo compositions that can inhibit copper depositing on hair, as well as facilitate the removal of copper already deposited thereon.